The present invention relates to a wheelchair having a main wheel such as a manual or powered mid-wheel drive wheel and also having at least one ground engaging front wheel containing a multiple biased suspension and anti-tip assembly.
Heretofore, mid-wheel drive wheels have had a front anti-tip wheel located up off or above the ground such as in the wheelchair disclosed in U.S. Pat. No. 5,944,131. Alternatively, U.S. Pat. No. 5,435,404 to Garin discloses a ground engaging front wheel and a rear caster wheel preferably attached to a vertically pivotal swing arm.
A mid-wheel drive wheelchair (either manual or power) has at least one resiliently biased ground engaging front wheel having a multiple suspension assembly to improve tracking upon undulating or irregular surfaces as well as improved anti-tip stability. The front wheel is a caster wheel pivotally attached to an arm directly or indirectly connected to the wheelchair frame. The front wheel desirably contains a dual spring suspension system wherein a primary spring has a preset compression and wherein a secondary spring has an adjustable compression to accommodate a range of individual body weights and personal performance preferences with regard to anti-tipping of the wheelchair. The secondary spring can be adjustable so that the compression thereof can partially overlap, be sequential, or have separate range than the primary spring.